1. Field of the Invention
The invention relates to an apparatus which has at least one vessel including at least one membrane for receiving samples.
2. Description of the Prior Art
Apparatus of this type are known, especially for use at laboratories. For instance, those are centrifugal filtration vessels in the form of a small tube with a filtering membrane which closes a bottom-sided aperture. The centrifugal filter cartridge is inserted in the upper region of a centrifuging vessel and is supported by an outer step thereof at the border of the filling aperture of the centrifuging vessel. A sample liquid poured into the centrifugal filtration vessel is filtered by the membrane during centrifuging. The filtered liquid passes into the centrifuging vessel through the membrane and the aperture and the filtration residue is retained by the membrane. It is known to loosely place the membrane on top of a perforated bottom of the filtration vessel U.S. Pat. No. 4,683,058). As a consequence, the liquid might flow past the membrane, particularly if the membrane slips away so as not to cause the filtering action which is desired.
In addition, it is known to fuse membranes, at their borders, to the bottom area of vessels. However, this presupposes that the material of the membrane and that of the vessel, which is mostly a plastic material, can be welded to each other. Furthermore, if different membrane thicknesses are used it is necessary to adapt the manufacturing process to them, which is relatively expensive.
Moreover, membrane panels are known which are panels made of a plastic including a multiplicity of receptacles which have an aperture at top and the bottom of which is closed by a membrane. The filtration of liquid samples using membrane panels, for instance, may be accomplished by suction devices which apply a negative pressure to the membrane side of the membrane panel to allow the filtrate to drip into a receiver arranged below the membrane panel. If membrane panels are used the membranes are inserted or welded in or are welded to the panel underside like in centrifugal filtration vessels.
Accordingly, it is the object of the invention to provide an apparatus for receiving samples which prevents the medium to be filtered from flowing past the membrane and enables the use of membranes made of different materials and exhibiting different dimensions. In addition, the intention is to provide a method for the manufacture of the apparatus.